1. Field of the Invention
The present invention relates to a color filter substrate, and a liquid crystal display panel comprising the color filter substrate stacked on a counter substrate through a seal material.
2. Background Art
A retardation film for controlling a phase difference has hitherto been used in liquid crystal displays. For example, in the reflection-type liquid crystal display, in general, a linearly polarizing plate and a ¼λ retardation plate are used in combination to provide circularly polarized light. Further, in recent years, in a liquid crystal display of a homeotropic alignment mode widely used in liquid crystal TV applications, in order to reduce the dependency of display upon the angle of visibility, a retardation film having an optical axis perpendicular to the substrate and having a negative birefringence anisotropy (a negative C plate) and a retardation film having an optical axis horizontal to the substrate and having a positive birefringence anisotropy (a positive A plate) are used in combination. Many other retardation films are commercially available including view angle compensation films using discotic liquid crystals.
All the above conventional retardation films are applied to the outer side of the liquid crystal cell. In this case, for the reason that different retardation films, or a retardation film and a polarizing plate are applied to each other at a certain specific angle and for the reason that the refractive index of a pressure-sensitive adhesive for application is different from the refractive index of the retardation plate and the refractive index of the polarizing plate, external light reflection occurs at the lamination interface, leading to lowered display contrast.
In recent years, an attempt has been made to provide a retardation layer utilizing a liquid crystal material within a liquid crystal cell (Japanese Patent Laid-Open No. 48627/1998). Such liquid crystal materials usable herein include, for example, liquid crystalline polymers having a glass transition point and capable of freezing the liquid crystal structure at or below the glass transition temperature, and liquid crystalline monomers which can cause three-dimensional crosslinking in a liquid crystal layer state utilizing a reactive group such as an unsaturated bond in a molecular structure and consequently can freeze the liquid crystal structure. The liquid crystal materials can be applied by coating onto a base material having an aligning function. The retardation layer provided within the liquid crystal cell can eliminate the drawbacks of conventional retardation films of a type applied to the outside of the liquid crystal cell.
When a retardation layer is provided on the inner side of the liquid crystal cell, the retardation layer is provided on any one of a pair of substrates constituting the liquid crystal cell. Typically, the retardation layer is provided on the inner side of a color filter substrate with a color filter. The liquid crystal cell is constructed so that a color filter substrate and a counter substrate are provided in combination and a liquid crystal material is filled into between the substrates. Both the substrates face each other while providing a given space therebetween, and the peripheral part of the substrates are sealed with a seal material.
When a retardation film is provided on the outer side of the liquid crystal cell as in the prior art, both the substrates on their inner sides (liquid crystal material filling sides) are intimately contacted with each other through a seal material. When a retardation layer is provided on the inner side of the liquid crystal cell, however, for the retardation layer, the black matrix, and the seal material, mutual positional relationship and mutual adhesion should be taken into consideration.
Originally, the provision of the black matrix, the color filter layer, and the retardation layer only in a part corresponding to the display part in the substrate suffices for contemplated results. Regarding the retardation layer, however, this layer is formed by coating and thus is preferably provided on the whole area or substantially the whole area of the substrate. On the other hand, the color filter layers are formed by patterning using a photosensitive resin composition upon ultraviolet irradiation and development so that the color layers are arranged in a predetermined array for each color in a large number of fine areas (patterning areas) surrounded by a black matrix. Therefore, in general, the color filter layers are formed only in the display part of the substrate. Further, for the black matrix, a picture frame part having a relatively large width is formed around the display part from the viewpoint of ensuring light shielding properties, that is, preventing light leakage toward the outside of the display part (lateral leakage).
The peripheral part of the display part is also a site which serves as a seal part to which the seal material is applied in the formation of the liquid crystal cell. Accordingly, when the width of the picture frame part of the black matrix is a certain value, in some cases, the seal part is formed so as to astride a picture frame part-provided part and a picture frame part-free part. When the seal part is provided in a level difference part, in coating the composition for seal material formation followed by heating, a difference in thermal shrinkage in a thickness-wise direction of the composition for seal material formation occurs between the case where the picture frame part of the black matrix is present as the layer underlying the seal material and the case where the picture frame part of the black matrix is absent as the layer underlying the seal material, and, consequently, distortion sometimes occurs within the seal material.